sendto:资源暂时不可用(errno 11)

I am having a problem with sendto.

我对sendto有问题。

I have a receiver who receives UPD packets with recvfrom and then replies to the sender using sendto.

我有一个接收方，它接收到带有recvfrom的UPD包，然后使用sendto对发送方进行回复。

Unfortunately, I am getting errno 11 (Resource temporarily unavailable). I am using two sockets.

不幸的是，我得到了errno 11(资源暂时不可用)。我用两个插座。

The first packet is actually sent but not the ones afterwards:

第一个包实际上是发送的，但不是之后的:

sendto :: Success

成功发送到:

error: 0.

错误:0。

sendto :: Resource temporarily unavailable

sendto::资源暂时不可用。

error: 11.

错误:11。

sendto :: Resource temporarily unavailable

sendto::资源暂时不可用。

...

…

This is an extract of my code:

这是我的代码摘录:

    int sockfd, sockSend;

    if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
            perror("socket");

    if ((sockSend = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
            perror("socket");

    if (fcntl(sockfd, F_SETOWN, getpid()) < 0) {
            perror("fcntl"); 
    }
    if (fcntl(sockfd, F_SETFL, O_RDONLY | O_NONBLOCK | FASYNC) < 0) {
            perror("fcntl"); 
    } 

    if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr))
                    < 0)
            perror("bind");

And in a SIGIO handler:

在SIGIO处理器中:

    len = sizeof(recv_addr);
    char buffer[payload];
    bzero(buffer, payload);
    n = recvfrom(sockfd, buffer, payload, MSG_DONTWAIT, (struct sockaddr *)&recv_addr, &len);

    while (n > 0) {

                            sprintf(response, "%d\n%d\n%d\n", items, target_buf, pb_sp);          
                            sendto(sockSend, response, strlen(response), 0, (struct sockaddr *) &recv_addr, sizeof(recv_addr));
                            // sleep(1);

                            perror("sendto :");
                            printf("error: %d.\n", errno);

     }

Could this issue come because the port is still hot, and I need to wait before reusing it? I've tried to change port but it hasn't helped.

这个问题是否会出现，因为这个端口仍然很热，我需要等待再使用它?我试过换港口，但没起什么作用。

Update: If the sleep(1) is commented out, then the packets actually get send!

更新:如果sleep(1)被注释掉，那么数据包实际上就会被发送!

Thanks a lot for your help.

非常感谢你的帮助。

2 个解决方案

#1

The error you are getting:

你得到的错误是:

EAGAIN or EWOULDBLOCK: The socket is marked nonblocking and the requested operation would block. POSIX.1-2001 allows either error to be returned for this case, and does not require these constants to have the same value, so a portable application should check for both possibilities.

You set the socket to non-blocking (O_NONBLOCK). The socket is still busy sending the previous message. You cannot send another until the first has finished sending. That's why sleeping helped.

将套接字设置为非阻塞(O_NONBLOCK)。套接字仍在忙于发送先前的消息。您不能发送另一个直到第一个完成发送。这就是为什么睡了。

Don't set it to non-blocking, or try again after select says you can.

不要将其设置为非阻塞，或者在select语句之后再尝试。

#2

If you have to set the socket to non-blocking, you can do it safely (and only?) using select:

如果您必须将套接字设置为非阻塞，您可以使用select来安全地(并且仅是?)

select() and pselect() allow a program to monitor multiple file descriptors, waiting until one or more of the file descriptors become "ready" for some class of I/O operation (e.g., input possible). A file descriptor is considered ready if it is possible to perform the corresponding I/O operation (e.g., read(2)) without blocking.

select()和pselect()允许一个程序监视多个文件描述符，等待一个或多个文件描述符“准备好”用于某些类I/O操作(例如，输入可能)。如果可以执行相应的I/O操作(例如，read(2))而不阻塞，则认为文件描述符已准备就绪。

#1